A hybrid electric vehicle uses both an internal combustion engine and an electric power supply. That is, the hybrid electric vehicle efficiently combines and uses power of the internal combustion engine and power of a motor. The hybrid electric vehicle uses both mechanical energy of an engine and electric energy of a battery and uses optimal operating areas, or speed ranges, of the engine and the motor, and recovers energy while braking. As a result, fuel efficiency can be improved and energy can be efficiently used.
The hybrid electric vehicle provides driving modes including an electric vehicle (EV) mode using only torque of the motor by connecting or releasing an engine clutch, a hybrid electric vehicle (HEV) mode using the torque of the motor as auxiliary torque while using the torque of the engine as a main torque, a regenerative braking mode for charging the battery by recovering braking and inertial energy through generation of the motor in braking or driving by inertia of the hybrid electric vehicle, and the like.
In recent years, as a method for effectively increasing the fuel efficiency of the hybrid electric vehicle, a research for applying a two-cylinder engine has been performed. However, since the two-cylinder engine has a problem in which vibration is excessive, a method of reducing the vibration is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.